Millions of Americans suffer from salivary gland dysfunction. Salivary fluid secretion is necessary for speaking, eating, and for maintaining oral health and the inability to produce adequate salivary fluid secretion results in a variety of conditions that together comprise a major health problem for a significant proportion of the population. Fluid secreting epithelia utilize a complex interplay of ion channels and transport mechanisms. Sustained fluid secretion requires an increase in intracellular calcium produced by sympathetic nerve stimulation of muscarinic receptors on salivary gland acinar cells. This increase in intracellular calcium activates calcium-sensitive potassium (K) and anion channels which, together, drive fluid secretion. Salivary glands contain two types of calcium-activatedK channels named IK1 and maxi-K. The gene encoding the IK1 channel (Kcnn4) has been identified and Kcnmal is a candidate gene for maxi- K. In spite of considerable effort, the specific roles for these two channels in salivary glands remain unknown. Complicating this issue is the preliminary, novel finding that the activation of IK1 channels inhibits maxi-K channel current. The long term goal of this project is to determine the physiological roles for these two types of K channels. Achieving this goal will require confirming the identity of the maxi-K gene and determining the mechanism of the interaction between them. It is hypothesized that these two channels are co-localized in parotid acinar cells with other proteins and interact directly or through a closely-apposed intermediary and may have different calcium and/or muscarinic sensitivities The calcium and muscarinic sensitivities of these two channels will be measured and their mechanism of interaction tested with a combination of patch clamp electrophysiology, optical, biochemical, and molecular biological techniques. The physiological roles of the two channels will be probed with various physiological measurements of mice deficient in the expression of the two K channelgenes.